This invention is directed to a process for removing iodine and iodide from an aqueous feed stream, and more particularly, to a process for more effectively and efficiently removing iodine and iodide from an aqueous solution using anion exchange resins.
Iodine has been used as a disinfectant for many years. It's use as a disinfectant for potable water has been restricted to short term or emergency use due to concerns of excess iodine in the human diet, especially for people with thyroid conditions.
Strong base anion exchange materials have been used for the recovery of iodine from mixed brines as well as in a process to remove both forms of iodine in water treatment processes.
U.S. Pat. No. 3,767,776 uses a quaternary ammonium anion exchange material in an organic solvent, in a liquid/liquid extraction, to remove iodides from strongly alkaline brines.
U.S. Pat. No. 2,157,508 relates to the recovery of iodine and iodide using a metasilicate capable of selectively removing iodide ion from salt solutions. U.S. Pat. No. 5,356,611 comprises a process for recovering iodine from a composition containing elemental iodine. The process requires iodine to be reduced to iodide before sorption on an anion exchange resin.
U.S. Pat. No. 5,366,636 uses a chelating resin to hold silver ions which react with iodide ions in water forming insoluble silver iodide.
U.S. Pat. No. 5,350,523 relates to a process for removing anions in a solution at a high temperature by having the anions adsorbed on an anion exchange resin. The strong base anion resin can operate at a much higher than conventional temperature because of an alkyl link between the quaternary amine group and the benzene ring of the structural resin.
U.S. Pat. No. 2,945,746 relates to a process for recovering iodides from aqueous solutions of salt brine with ion exchange resins. The anionic exchange resins are eluted with an acidified salt solution containing traces of SO.sub.2.
U.S. Pat. No. 2,261,021 relates to the sorption of free elemental iodine from aqueous solutions using a resin made by the condensation of metaphenylene diamine and formaldehyde.
U.S. Pat. No. 3,050,369 relates to a process for recovering iodine from aqueous iodide solutions, by contacting an aqueous iodide solution with a trimethyl amine anion exchange resin, such as Dowex.RTM. 1, 2, 11 or 21A, in a polyhalide form.
U.S. Pat. No. 3,177,050 describes a fluidized ion exchange bed including an anion exchange resin for recovering iodine from an aqueous solution. The resin employed is a commercial, strongly basic, quaternary ammonium anion exchange resin. A particular resin employed is a trimethyl quaternary ammonium anion exchange resin.
Strong-base anion resins have also been used to separate nitrate from waters containing a significant amount of sulfate ion. In U.S. Pat. No. 4,479,877, for example, nitrate removal is accomplished by passing the water to be treated through a bed of a strong-base anion exchange resin which is a tributyl amine derivative of a copolymer exemplified by styrene-divinyl benzene.